In the event of an oblique collision accident in which an opponent object collides with an own vehicle obliquely from a front end of the vehicle, an occupant is pushed and moved obliquely forwardly from his/her initial position (seated position). With a view to protecting an occupant in the event of such an oblique collision accident, there has heretofore been employed a technique of deploying airbags from both front and lateral sides of the occupant.
For example, a vehicle disclosed in JP 2013-133049A (hereinafter referred to as “Patent Literature 1”) is equipped with a front airbag configured to be deployed rearwardly from an instrument panel disposed at a front end of a passenger compartment, and a side airbag configured to be deployed downwardly from a lateral edge portion (a pillar or a roof side rail) of an upper wall of the passenger compartment. In the above airbag apparatus disclosed in the Patent Literature 1, even in a situation where an occupant is pushed and moved obliquely forwardly due to an oblique collision, the front airbag and the side airbag can receive a head region of the occupant to achieve protection of the occupant.
Further, with a view to protecting an occupant using only a front airbag during an oblique collision, there has also been invented a technique of deploying the front airbag to form a bilaterally asymmetric configuration. Heretofore-known examples thereof include JP 2008-044594A (hereinafter referred to as “Patent Literature 2”). Specifically, an airbag apparatus disclosed in the Patent Literature 2 comprises an airbag configured to be deployed rearwardly from an instrument panel toward an occupant, a pair of locking members disengageably engageable with respect to right and left tethers provided inside the airbag, and an actuator configured to drive the pair of locking members individually, depending on a type of vehicle collision. The actuator is operable, upon detection of an oblique collision of a vehicle, to drive only one of the pair of locking members in such a manner as to release a locked state of one of the tethers closer to an opponent object and maintain a locked state of the other tether farther away from the opponent object. Thus, the front airbag is deployed such that a lateral portion thereof closer to the opponent object is inflated rearwardly to a larger extent than a lateral portion thereof farther away from the opponent object, so that it becomes possible to protect an occupant (who is pushed and moved toward a side closer to the opponent object, under an impact during the oblique collision) by the rearwardly largely inflated portion.
However, the airbag apparatus disclosed in the Patent Literature 1 is likely to fail to adequately receive (sufficiently restrain) an occupant on a case-by-case basis. For example, it is assumed that, when a head region of the occupant hits against the front airbag in an obliquely forward direction, the front airbag is deformed such that a rear surface thereof largely inclines in response to an obliquely forwardly-oriented load input from the occupant's head region to the front airbag. Once such a deformation occurs, the occupant's head region is more likely to be displaced laterally along the rear surface of the front airbag (i.e., displaced from a central region to a peripheral edge region of the front airbag), leading to a risk that the front airbag becomes unable to receive the occupant's head region with a sufficient force, resulting in failing to achieve adequate protection of the occupant.
The airbag apparatus disclosed in the Patent Literature 2 has a potential to prevent the lateral displacement of the occupant's head region because the airbag is deployed to form a bilaterally asymmetric configuration. However, in order to deploy the airbag to form in a bilaterally asymmetric configuration (selectively restrain either one of the right and left tethers), it is necessary to select either one of the right and left locking members and drive the selected locking member at an appropriate timing. In other word, if the drive timing is deviated even just slightly, it becomes impossible to realize an intended bilaterally asymmetric configuration. Thus, there remains a need for improvement in terms of certainty of the protection. Moreover, the lateral portion of the airbag closer to the opponent object needs to be largely inflated rearwardly, and accordingly an internal volume of the airbag is increased, so that a time required for deployment becomes longer, leading to a risk of becoming unable to adequately protect an occupant.